Laser addressable thermal transfer imaging element with an interlayer

ABSTRACT

A thermal transfer donor element is provided which comprises a support, a light-to-heat conversion layer, an interlayer, and a thermal transfer layer. When the above donor element is brought into contact with a receptor and imagewise irradiated, an image is obtained which is free from contamination by the light-to-heat conversion layer. The construction and process of this invention is useful in making colored images including applications such as color proofs and color filter elements.

[0001] This is a continuation of Ser. No. 09/553,294, filed Apr. 20,2000, which is a continuation of Ser. No. 09/349,329, now U.S. Pat. No.6,099,994, filed Jul. 8, 1999, which is a continuation of Ser. No.09/031,941, now U.S. Pat. No. 5,981,136, filed Feb. 27, 1998, which is adivisional of Ser. No. 08/632,225, now U.S. Pat. No. 5,725,898, filedApr. 15, 1996.

FIELD OF INVENTION

[0002] This invention relates to thermal transfer imaging elements, inparticular, to laser addressable thermal transfer elements having aninterlayer between a radiation-absorbing/thermal conversion layer and atransferable layer. In addition, the invention relates to a method ofusing the thermal transfer element in a thermal transfer system such asa laser addressable system.

BACKGROUND

[0003] With the increase in electronic imaging information capacity anduse, a need for imaging systems capable of being addressed by a varietyof electronic sources is also increasing. Examples of such imagingsystems include thermal transfer, ablation (or transparentization) andablation-transfer imaging. These imaging systems have been shown to beuseful in a wide variety of applications, such as, color proofing, colorfilter arrays for liquid crystal display devices, printing plates, andreproduction masks. The traditional method of recording electronicinformation with a thermal transfer imaging medium utilizes a thermalprinthead as the energy source. The information is transmitted aselectrical energy to the printhead causing a localized heating of athermal transfer donor sheet which then transfers material correspondingto the image data to a receptor sheet. The two primary types of thermaltransfer donor sheets are dye sublimation (or dye diffusion transfer)and thermal mass transfer. Representative examples of these types ofimaging systems can be found in U.S. Pat. Nos. 4,839,224 and 4,822,643.The use of thermal printheads as an energy source suffers severaldisadvantages, such as, size limitations of the printhead, slow imagerecording speeds (milliseconds), limited resolution, limitedaddressability, and artifacts on the image from detrimental contact ofthe media with the printhead.

[0004] The increasing availability and use of higher output compactlasers, semiconductor light sources, laser diodes and other radiationsources which emit in the ultraviolet, visible and particularly in thenear-infrared and infrared regions of the electromagnetic spectrum, haveallowed the use of these sources as viable alternatives for the thermalprinthead as an energy source. The use of a radiation source such as alaser or laser diode as the imaging source is one of the primary andpreferred means for transferring electronic information onto an imagerecording media. The use of radiation to expose the media provideshigher resolution and more flexibility in format size of the final imagethan the traditional thermal printhead imaging systems. In addition,radiation sources such as lasers and laser diodes provide the advantageof eliminating the detrimental effects from contact of the media withthe heat source. As a consequence, a need exists for media that have theability to be efficiently exposed by these sources and have the abilityto form images having high resolution and improved edge sharpness.

[0005] It is well known in the art to incorporate light-absorbing layersin thermal 20 transfer constructions to act as light-to-heat converters,thus allowing non-contact imaging using radiation sources such as lasersand laser diodes as energy sources. Representative examples of thesetypes of elements can be found in U.S. Pat. Nos. 5,308,737; 5,278,023;5,256,506; and 5,156,938. The transfer layer may contain light absorbingmaterials such that the transfer layer itself functions as thelight-to-heat conversion layer. Alternatively, the light-to-heatconversion layer may be a separate layer, for instance, a separate layerbetween the substrate and the transfer layer. Constructions in which thetransfer layer itself functions as the light-to-heat conversion layermay require the addition of an additive to increase the absorption ofincident radiation and effect transfer to a receptor. In these cases,the presence of the absorber in the transferred image may have adetrimental effect upon the performance of the imaged object (e.g.,visible absorption which reduces the optical purity of the colors in thetransferred image, reduced transferred image stability, incompatibilitybetween the absorber and other components present in the imaging layer,etc.).

[0006] Contamination of the transferred image by the light-to-heatconversion layer itself is often observed when using donor constructionshaving a separate light-to-heat conversion layer. In the cases wherecontamination of the transferred image by such unintended transfer ofthe light-to-heat conversion layer occurs and the light-to-heatconversion layer possesses an optical absorbance that interferes withthe performance of the transferred image (e.g., transfer of a portion ofa black body light-to-heat conversion layer to a color filter array orcolor proof), the incidental transfer of the light-to-heat conversionlayer to the receptor is particularly detrimental to quality of theimaged article. Similarly, mechanical or thermal distortion of thelight-to-heat conversion layer during imaging is common and negativelyimpacts the quality of the transferred coating. U.S. Pat. No. 5,171,650discloses methods and materials for thermal imaging using an“ablation-transfer” technique. The donor element used in the imagingprocess comprises a support, an intermediate dynamic release layer, andan ablative carrier topcoat containing a colorant. Both the dynamicrelease layer and the color carrier layer may contain aninfrared-absorbing (light to heat conversion) dye or pigment. A coloredimage is produced by placing the donor element in intimate contact witha receptor and then irradiating the donor with a coherent light sourcein an imagewise pattern. The colored carrier layer is simultaneouslyreleased and propelled away from the dynamic release layer in the lightstruck areas creating a colored image on the receptor.

[0007] Co-pending U.S. application Ser. No. 07/855,799 filed Mar. 23,1992 discloses ablative imaging elements comprising a substrate coatedon a portion thereof with an energy sensitive layer comprising aglycidyl azide polymer in combination with a radiation absorber.Demonstrated imaging sources included infrared, visible, and ultravioletlasers. Solid state lasers were disclosed as exposure sources, althoughlaser diodes were not specifically mentioned. This application isprimarily concerned with the formation of relief printing plates andlithographic plates by ablation of the energy sensitive layer. Nospecific mention of utility for thermal mass transfer was made.

[0008] U.S. Pat. No. 5,308,737 discloses the use of black metal layerson polymeric substrates with gas-producing polymer layers which generaterelatively high volumes of gas when irradiated. The black metal (e.g.,black aluminum) absorbs the radiation efficiently and converts it toheat for the gas-generating materials. It is observed in the examplesthat in some cases the black metal was eliminated from the substrate,leaving a positive image on the substrate.

[0009] U.S. Pat. No. 5,278,023 discloses laser-addressable thermaltransfer materials for producing color proofs, printing plates, films,printed circuit boards, and other media. The materials contain asubstrate coated thereon with a propellant layer wherein the propellantlayer contains a material capable of producing nitrogen (N₂) gas at atemperature of preferably less than about 300° C.; a radiation absorber;and a thermal mass transfer material. The thermal mass transfer materialmay be incorporated into the propellant layer or in an additional layercoated onto the propellant layer. The radiation absorber may be employedin one of the above-disclosed layers or in a separate layer in order toachieve localized heating with an electromagnetic energy source, such asa laser. Upon laser induced heating, the transfer material is propelledto the receptor by the rapid expansion of gas. The thermal mass transfermaterial may contain, for example, pigments, toner particles, resins,metal particles, monomers, polymers, dyes, or combinations thereof. Alsodisclosed is a process for forming an image as well as an imaged articlemade thereby.

[0010] Laser-induced mass transfer processes have the advantage of veryshort heating times (nanoseconds to microseconds); whereas, theconventional thermal mass transfer methods are relatively slow due tothe longer dwell times (milliseconds) required to heat the printhead andtransfer the heat to the donor. The transferred images generated underlaser-induced ablation imaging conditions are often fragmented (beingpropelled from the surface as particulates or fragments). The imagesfrom thermal melt stick transfer systems tend to show deformities on thesurface of the transferred material. Therefore, there is a need for athermal transfer system that takes advantage of the speed and efficiencyof laser addressable systems without sacrificing image quality orresolution.

SUMMARY OF THE INVENTION

[0011] The present invention relates to a thermal transfer elementcomprising a substrate having deposited thereon (a) a light-to-heatconversion layer, (b) an interlayer, and (c) a thermal transfer layer.The thermal transfer layer may additionally comprise crosslinkablematerials.

[0012] The present invention also provides a method for generating animage on a receptor using the above described thermal transfer element.An image is transferred onto a receptor by (a) placing in intimatecontact a receptor and the thermal transfer element described above, (b)exposing the thermal transfer element in an imagewise pattern with aradiation source, and (c) transferring the thermal transfer layercorresponding to the imagewise pattern to the receptor, withinsignificant or no transfer of the light-to-heat conversion layer. Whenthe thermal transfer layer contains crosslinkable materials, anadditional curing step may be performed where the transferred image issubsequently crosslinked by exposure to heat or radiation, or treatmentwith chemical curatives.

[0013] The phrase “in intimate contact” refers to sufficient contactbetween two surfaces such that the transfer of materials may beaccomplished during the imaging process to provide a sufficient transferof material within the thermally addressed areas. In other words, novoids are present in the imaged areas which would render the transferredimage non-functional in its intended application.

[0014] Other aspects, advantages, and benefits of the present inventionare apparent from the detailed description, the examples, and theclaims.

DETAILED DESCRIPTION OF INVENTION

[0015] A thermal transfer element is provided comprising a lighttransparent substrate having deposited thereon, in the following order,a light-to-heat conversion (LTHC) layer, a heat stable interlayer, and athermal transfer layer. The substrate is typically a polyester film, forexample, poly(ethylene terephthalate) or poly(ethylene naphthalate).However, any film that has appropriate optical properties and sufficientmechanical stability can be used.

[0016] Light-to-heat Conversion Layer

[0017] In order to couple the energy of the exposure source into theimaging construction it is especially desirable to incorporate alight-to-heat conversion (LTHC) layer within the construction. The LTHClayer comprises a material which absorbs at least at the wavelength ofirradiation and converts a portion of the incident radiation intosufficient heat to enable transfer the thermal transfer layer from thedonor to the receptor. Typically, LTHC layers will be absorptive in theinfrared region of the electromagnetic spectrum, but in some instancesvisible or ultraviolet absorptions may be selected. It is generallydesirable for the radiation absorber to be highly absorptive of theimaging radiation, enabling an optical density at the wavelength of theimaging radiation in the range of 0.2 to 3.0 using a minimum amount ofradiation absorber to be used.

[0018] Dyes suitable for use as radiation absorbers in a LTHC layer maybe present in particulate form or preferably substantially in moleculardispersion. Especially preferred are dyes absorbing in the IR region ofthe spectrum. Examples of such dyes may be found in Matsuoka, M.,Infrared Absorbing Materials, Plenum Press, New York, 1990, and inMatsuoka, M., Absorption Spectra of Dyes for Diode Lasers, BunshinPublishing Co., Tokyo, 1990. IR absorbers marketed by American Cyanamidor Glendale Protective Technologies, Inc., Lakeland, Fla., under thedesignation CYASORB IR-99, IR-126 and IR-165 may also be used. Such dyeswill be chosen for solubility in, and compatibility with, the specificpolymer and coating solvent in question.

[0019] Pigmentary materials may also be dispersed in the LTHC layer foruse as radiation absorbers. Examples include carbon black and graphiteas well as phthalocyanines, nickel dithiolenes, and other pigmentsdescribed in U.S. Pat. Nos. 5,166,024 and 5,351,617. Additionally, blackazo pigments based on copper or chromium complexes of, for example,pyrazolone yellow, dianisidine red, and nickel azo yellow are useful.Inorganic pigments are also valuable. Examples include oxides andsulfides of metals such as aluminum, bismuth, tin, indium, zinc,titanium, chromium, molybdenum, tungsten, cobalt, iridium, nickel,palladium, platinum, copper, silver, gold, zirconium, iron, lead ortellurium. Metal borides, carbides, nitrides, carbonitrides,bronze-structured oxides, and oxides structurally related to the bronzefamily (e.g. WO_(2.9)) are also of utility.

[0020] When dispersed particulate radiation absorbers are used, it ispreferred that the particle size be less than about 10 micrometers, andespecially preferred that the particle size be less than about 1micrometer. Metals themselves may be employed, either in the form ofparticles, as described for instance in U.S. Pat. No. 4,252,671, or asfilms as disclosed in U.S. Pat. No. 5,256,506. Suitable metals includealuminum, bismuth, tin, indium, tellurium and zinc.

[0021] Suitable binders for use in the LTHC layer include film-formingpolymers, such as for example, phenolic resins (i.e., novolak and resoleresins), polyvinyl butyral resins, polyvinylacetates, polyvinyl acetals,polyvinylidene chlorides, polyacrylates, cellulosic ethers and esters,nitrocelluloses, and polycarbonates. The absorber-to-binder ratio isgenerally from 5:1 to 1:100 by weight depending on what type ofabsorbers and binders are used. Conventional coating aids, such assurfactants and dispersing agents, may be added to facilitate thecoating process. The LTHC layer may be coated onto the substrate using avariety of coating methods known in the art. The LTHC layer is coated toa thickness of 0.001 to 20.0 micrometers, preferably 0.01 to 5.0micrometers. The desired thickness of the LTHC layer will depend uponthe composition of the layer. A preferred LTHC layer is a pigment/binderlayer. A particularly preferred pigment based LTHC layer is carbon blackdispersed in an organic polymeric binder. Alternatively, other preferredLTHC layers include metal or metal/metal oxide layers (e.g. blackaluminum which is a partially oxidized aluminum having a black visualappearance).

[0022] Interlayer Construction

[0023] The interlayer may comprise an organic and/or inorganic material.In order to minimize damage and contamination of the resultanttransferred image, the interlayer should have high thermal resistance.Preferably, the layer should not visibly distort or chemically decomposeat temperatures below 150° C. These properties may be readily providedby polymeric film (thermoplastic or thermoset layers), metal layers(e.g., vapor deposited metal layers), inorganic layers (e.g., sol-geldeposited layers, vapor deposited layers of inorganic oxides [e.g.,silica, titania, etc., including metal oxides]), and organic/inorganiccomposite layers (thermoplastic or thermoset layers). Organic materialssuitable as interlayer materials include both thermoset (crosslinked)and thermoplastic materials. In both cases, the material chosen for theinterlayer should be film forming and should remain substantially intactduring the imaging process. This can be accomplished by the properselection of materials based on their thermal and/or mechanicalproperties. As a guideline, the T_(g) of the thermoplastic materialsshould be greater than 150° C., more preferably greater than 180° C. Theinterlayer may be either transmissive, absorbing, reflective, or somecombination thereof at the imaging radiation wavelength.

[0024] The surface characteristics of the interlayer will depend on theapplication for which the imaged article is to be used. Frequently, itwill be desirable to have an interlayer with a “smooth” surface so asnot to impart adverse texture to the surface of the thermallytransferred layer. This is especially important for applicationsrequiring rigid dimensional tolerances such as for color filter elementsfor liquid crystal displays. However, for other applications surface“roughness” or “surface patterns” may be tolerable or even desirable.

[0025] The interlayer provides a number of desirable benefits. Theinterlayer is essentially a barter against the transfer of material fromthe light-to-heat conversion layer. The interlayer can also preventdistortion of the transferred thermal transfer layer material. It mayalso modulate the temperature attained in the thermal transfer layer sothat more thermally unstable materials can be transferred and may alsoresult in improved plastic memory in the transferred material. It isalso to be noted that the interlayer of the present invention, whenplaced over the LTHC layer, is incompatible with propulsively ablativesystems like those of U.S. Pat. Nos. 5,156,938; 5,171,650; and 5,256,506because the interlayer would act as a barrier to prevent propulsiveforces from the LTHC layer from acting on the thermal transfer layer.The gas-generating layers disclosed in those patents also would notqualify as interlayers according to the present invention, as thoselayers must be thermally unstable at the imaging temperatures todecompose and generate the gas to propel material from the surface.

[0026] Suitable thermoset resins include materials which may becrosslinked by thermal, radiation, or chemical treatment including, butnot limited to, crosslinked poly(meth)acrylates, polyesters, epoxies,polyurethanes, etc. For ease of application, the thermoset materials areusually coated onto the light-to-heat conversion layer as thermoplasticprecursors and subsequently crosslinked to form the desired crosslinkedinterlayer.

[0027] In the case of thermoplastic materials, any material which meetsthe above-mentioned functional criteria may be employed as an interlayermaterial. Accordingly, the preferred materials will possess chemicalstability and mechanical integrity under the imaging conditions. Classesof preferred thermoplastic materials include polysulfones, polyesters,polyimides, etc. These thermoplastic organic materials may be applied tothe light-to-heat conversion layer via conventional coating techniques(solvent coating, etc.).

[0028] In the cases of interlayers comprised of organic materials, theinterlayers may also contain appropriate additives includingphotoinitiators, surfactants, pigments, plasticizers, coating aids, etc.The optimum thickness of an organic interlayer is material dependentand, in general, will be the minimum thickness at which transfer of thelight-to-heat conversion layer and distortion of the transferred layerare reduced to levels acceptable for the intended application (whichwill generally be between 0.05 μm and 10 μm).

[0029] Inorganic materials suitable as interlayer materials includemetals, metal oxides, metal sulfides, inorganic carbon coatings, etc.,including those which are highly transmissive or reflective at theimaging laser wavelength. These materials may be applied to thelight-to-heat-conversion layer via conventional techniques (e.g., vacuumsputtering, vacuum evaporation, plasma jet, etc.). The optimum thicknessof an inorganic interlayer will again be material dependent. The optimumthickness will be, in general, the minimum thickness at which transferof the light-to-heat conversion layer and distortion of the transferredlayer are reduced to an acceptable level (which will generally bebetween 0.01 μm and 10 μm).

[0030] In the case of reflective interlayers, the interlayer comprises ahighly reflective material, such as aluminum or coatings of TiO₂ basedinks. The reflective material should be capable of forming animage-releasing surface for the overlying colorant layer and shouldremain intact during the colorant coating process. The interlayer shouldnot melt or transfer under imaging conditions. In the case where imagingis performed via irradiation from the donor side, a reflectiveinterlayer will attenuate the level of imaging radiation transmittedthrough the interlayer and thereby reduce any damage to the resultantimage that might result from interaction of the transmitted radiationwith the transfer layer and/or receptor. This is particularly beneficialin reducing thermal damage to the transferred image which might occurwhen the receptor is highly absorptive of the imaging radiation.Optionally, the thermal transfer donor element may comprise severalinterlayers, for example, both a reflective and transmissive interlayer,the sequencing of which would be dependent upon the imaging and end-useapplication requirements.

[0031] Suitable highly reflective metallic films include aluminum,chrome, and silver. Suitable pigment based inks include standard whitepigments such as titanium dioxide, calcium carbonate, and barium sulfateused in conjunction with a binder. The binder may be either athermoplastic or thermoset material. Preferred binders include highT_(g) resins such as polysulfones, polyarylsulfones,polyarylethersulfones, polyetherimides, polyarylates, polyimides,polyetheretherketones, and polyamideimides (thermoplastics) andpolyesters, epoxies, polyacrylates, polyurethanes, phenol-formaldehydes,urea-formaldehydes, and melamine-formaldehydes (thermosets), etc.

[0032] Polymerizable or crosslinkable monomers, oligomers, prepolymersand polymers may be used as binders and crosslinked to form the desiredheat-resistant, reflective interlayer after the coating process. Themonomers, oligomers, prepolymers and polymers that are suitable for thisapplication include known chemicals that can form a heat resistantpolymeric layer. The layer may also contain additives such ascrosslinkers, surfactants, coating aids, and pigments.

[0033] The reflective layer thickness can be optimized with respect toimaging performance, sensitivity, and surface smoothness. Normally thethickness of the interlayer is 0.005 to 5 microns, preferably between0.01 to 2.0 microns. Optionally, the reflective interlayer may beovercoated with a non-pigmented polymeric interlayer to allow a betterrelease of color image.

[0034] Thermal Transfer Layer

[0035] The transfer layer is formulated to be appropriate for thecorresponding imaging application (e.g., color proofing, printing plate,color filters, etc.). The transfer layer may itself be comprised ofthermoplastic and/or thermoset materials. In many product applications(for example, in printing plate and color filter applications) thetransfer layer materials are preferably crosslinked after laser transferin order to improve performance of the imaged article. Additivesincluded in the transfer layer will again be specific to the end-useapplication (e.g., colorants for color proofing and color filterapplications, photoinitiators for photo-crosslinked orphoto-crosslinkable transfer layers, etc.,) and are well known to thoseskilled in the art.

[0036] Because the interlayer can modulate the temperature attained inthe thermal transfer layer, materials which tend to be more sensitive toheat than typical pigments may be transferred with reduced damage usingthe process of the present invention. For example, medical diagnosticchemistry can be included in a binder and transferred to a medical testcard using the present invention with less likelihood of damage to themedical chemistry and less possibility of corruption of the testresults. A chemical or enzymatic indicator would be less likely to bedamaged using the present invention with an interlayer compared to thesame material transferred from a conventional thermal donor element.

[0037] The thermal transfer layer may comprise classes of materialsincluding, but not limited to dyes (e.g., visible dyes, ultravioletdyes, fluorescent dyes, radiation-polarizing dyes, IR dyes, etc.),optically active materials, pigments (e.g., transparent pigments,colored pigments, black body absorbers, etc.), magnetic particles,electrically conducting or insulating particles, liquid crystalmaterials, hydrophilic or hydrophobic materials, initiators,sensitizers, phosphors, polymeric binders, enzymes, etc. For manyapplications such as color proofing and color filter elements, thethermal transfer layer will comprise colorants. Preferably the thermaltransfer layer will comprise at least one organic or inorganic colorant(i.e., pigments or dyes) and a thermoplastic binder. Other additives mayalso be included such as an IR absorber, dispersing agents, surfactants,stabilizers, plasticizers, crosslinking agents and coating aids. Anypigment may be used, but for applications such as color filter elements,preferred pigments are those listed as having good color permanency andtransparency in the NPIRI Raw Materials Data Handbook, Volume 4(Pigments) or W. Herbst, Industrial Organic Pigments, VCH, 1993. Eithernon-aqueous or aqueous pigment dispersions may be used. The pigments aregenerally introduced into the color formulation in the form of amillbase comprising the pigment dispersed with a binder and suspendedinto a solvent or mixture of solvents. The pigment type and color arechosen such that the color coating is matched to a preset color targetor specification set by the industry. The type of dispersing resin andthe pigment-to-resin ratio will depend upon the pigment type, surfacetreatment on the pigment, dispersing solvent and milling process used ingenerating the millbase. Suitable dispersing resins include vinylchloride/vinyl acetate copolymers, poly(vinyl acetate)/crotonic acidcopolymers, polyarethanes, styrene maleic anhydride half ester resins,(meth)acrylate polymers and copolymers, poly(vinyl acetals), poly(vinylacetals) modified with anhydrides and amines, hydroxy alkyl celluloseresins and styrene acrylic resins. A preferred color transfer coatingcomposition comprises 30-80% by weight pigment, 15-60% by weight resin,and 0-20% by weight dispersing agents and additives.

[0038] The amount of binder present in the color transfer layer is keptto a minimum to avoid loss of image resolution and/or imagingsensitivity due to excessive cohesion in the color transfer layer. Thepigment-to-binder ratio is typically between 10:1 to 1:10 by weightdepending on the type of pigments and binders used. The binder systemmay also include polymerizable and/or crosslinkable materials (i.e.,monomers, oligomers, prepolymers, and/or polymers) and optionally aninitiator system. Using monomers or oligomers assists in reducing thebinder cohesive force in the color transfer layer, therefore improvingimaging sensitivity and/or transferred image resolution. Incorporationof a crosslinkable composition into the color transfer layer allows oneto produce a more durable and solvent resistant image. A highlycrosslinked image is formed by first transferring the image to areceptor and then exposing the transferred image to radiation, heatand/or a chemical curative to crosslink the polymerizable materials. Inthe case where radiation is employed to crosslink the composition, anyradiation source can be used that is absorbed by the transferred image.Preferably the composition comprises a composition which may becrosslinked with an ultraviolet radiation source.

[0039] The color transfer layer may be coated by any conventionalcoating method known in the art. It may be desirable to add coating aidssuch as surfactants and dispersing agents to provide an uniform coating.Preferably, the layer has a thickness from about 0.05 to 10.0micrometers, more preferably from 0.5 to 2.0 micrometers.

[0040] Receiver

[0041] The image receiving substrate may be any substrate suitable forthe application including, but not limited to, various papers,transparent films, LCD black matrices, active portions of LCD displays,metals, etc. Suitable receptors are well known to those skilled in theart. Non-limiting examples of receptors which can be used in the presentinvention include anodized aluminum and other metals, transparentplastic films (e.g., PET), glass, and a variety of different types ofpaper (e.g., filled or unfilled, calendered, coated, etc.). Variouslayers (e.g., an adhesive layer) may be coated onto the image receivingsubstrate to facilitate transfer of the transfer layer to the receiver.

[0042] Imaging Process

[0043] The process of the present invention may be performed by fairlysimple steps. During imaging, the donor sheet is brought into intimatecontact with a receptor sheet under pressure or vacuum. A radiationsource is then used to heat the LTHC layer in an imagewise fashion(e.g., digitally, analog exposure through a mask, etc.) or to performimagewise transfer of the thermal transfer layer from the donor to thereceptor.

[0044] The interlayer reduces the transfer of the LTHC layer to thereceptor and/or reduces distortion in the transferred layer. Withoutthis interlayer in thermal mass transfer processes addressed byradiation sources, the topography of the transfer surface from thelight-to-heat conversion layer may be observably altered. A significanttopography of deformations and wrinkles may be formed. This topographymay be imprinted on the transferred donor material. This imprinting ofthe image alters the reflectivity of the transferred image (rendering itless reflective than intended) and can cause other undesirable visualeffects. It is preferred that under imaging conditions, the adhesion ofthe interlayer to the LTHC layer be greater than the adhesion of theinterlayer to the thermal transfer layer. In the case where imaging isperformed via irradiation from the donor side, a reflective interlayerwill attenuate the level of imaging radiation transmitted through theinterlayer and thereby reduce any transferred image damage that mayresult from interaction of the transmitted radiation with the transferlayer and/or the receptor. This is particularly beneficial in reducingthermal damage which may occur to the transferred image when thereceptor is highly absorptive of the imaging radiation.

[0045] A variety of light-emitting sources can be utilized in thepresent invention. Infrared, visible, and ultraviolet lasers areparticularly useful when using digital imaging techniques. When analogtechniques are used (e.g., exposure through a mask) high powered lightsources (e.g, xenon flash lamps, etc.) are also useful. Preferred lasersfor use in this invention include high power (>100 mW) single mode laserdiodes, fiber-coupled laser diodes, and diode-pumped solid state lasers(e.g., Nd:YAG and Nd:YLF). Laser exposure dwell times should be fromabout 0.1 to 5 microseconds and laser fluences should be from about 0.01to about 1 Joules/cm².

[0046] During laser exposure, it may be desirable to minimize formationof interference patterns due to multiple reflections from the imagedmaterial. This can be accomplished by various methods. The most commonmethod is to effectively roughen the surface of the donor material onthe scale of the incident radiation as described in U.S. Pat. No.5,089,372. This has the effect of disrupting the spatial coherence ofthe incident radiation, thus minimizing self interference. An alternatemethod is to employ the use of an antireflection coating on the secondinterface that the incident illumination encounters. The use ofanti-reflection coatings is well known in the art, and may consist ofquarter-wave thicknesses of a coating such as magnesium fluoride, asdescribed in U.S. Pat. No. 5,171,650. Due to cost and manufacturingconstraints, the surface roughening approach is preferred in manyapplications.

[0047] The following non-limiting examples further illustrate thepresent invention.

EXAMPLES

[0048] Materials used in the following examples are available fromstandard commercial sources such as Aldrich Chemical Co. (Milwaukee,Wis.) unless otherwise specified. The preparation of hydantoinhexacrylate used in Example 2 is described for Compound A in U.S. Pat.Nos. 4,249,011 and 4,262,072.

[0049] Laser Imaging Procedure A

[0050] The colorant coating side of a thermal transfer donor was held inintimate contact with a 75 mm×50 mm×1 mm glass slide (receptor) in avacuum chuck such that the laser was incident upon the substrate (PET)side of the donor and normal to the donor/receptor surface. The vacuumchuck was attached to an X-Y translation stage such that it could bescanned in the plane of the donor/receptor surface, allowing laserexposure over the entire surface. A CW(continuous wave) Nd:YAG lasersystem was used for exposure, providing up to 14.5 Watts at 1064 nm inthe film plane. The laser had a Gaussian spatial profile with the spotsize tailored using external optics. An acoustic-optic modulator allowedcontrol of the laser power from ˜0 to 80%, the laser pulse width from˜20 ns to CW. The X-Y stage and laser power, pulse width and repetitionrate were computer controlled allowing programmed patterns to be imaged.

[0051] Laser Imaging Procedure B

[0052] The colorant coating side of a thermal transfer donor was held inintimate contact with a 75 mm×50 mm×1 mm glass slide (receptor) in avacuum chuck such that the laser was incident upon the substrate (PET)side of the donor. The vacuum chuck was attached to a one dimensionaltranslation stage such that it could be scanned in the plane of thedonor/receptor surface, allowing laser exposure over the entire surface.An optical system comprised of a CW Nd:YAG laser, acousto-opticmodulator, collimating and beam expanding optics, an optical isolator, alinear galvanometer and an f-theta scan lens was utilized. The Nd:YAGlaser was operating in the TEM 00 mode, and produced a total power of7.5 Watts on the image plane. Scanning was accomplished with the highprecision linear Cambridge Technology Galvonometer. The laser wasfocused to a Gaussian spot with a measured diameter of 140 microns atthe 1/e² intensity level. The spot was held constant across the scanwidth by utilizing an f-theta scan lens. The laser spot was scannedacross the image surface at a velocity of 7.92 meters/second. Thef-theta scan lens held the scan velocity uniform to within 0.1%, and thespot size constant to within ±3 microns.

Example 1

[0053] (Comparative Example)

[0054] This example demonstrates the preparation and use of a thermaltransfer donor without an interlayer.

[0055] A black aluminum (partially oxidized Al, AlO_(X)) light-to-heatconversion layer with a transmission optical density (TOD=−logT, where Tis the measured fractional transmission) of 0.53 at 1060 nm was coatedonto a 4 mil poly(ethylene terephthalate) (PET) substrate via reactivesputtering of Al in an Ar/O₂ atmosphere in a continuous vacuum coateraccording to the teachings of U.S. Pat. No. 4,430,366. This AlO_(X)light-to-heat conversion layer was then overcoated with a red color inkwith 26.5 weight % total nonvolatiles content (CRY-S089, produced byFuji-Hunt Electronics Technology Co., LTD, Tokyo, Japan) using a #5coating rod and dried to produce a thermal transfer donor.

[0056] This donor was then tested for transfer of the thermal transferlayer to a glass slide receptor, which had been precoated with a vinylacrylic copolymer (Wallpol 40148-00, Reichhold Chemicals, Inc. ResearchTriangle Park, N.C.). The above-described Laser Imaging Procedure A wasemployed, the laser spot size diameter (1/e²) was 100 μm, the power atthe film plane was 8.4 Watts, and exposures were performed at pulsewidths of 4, 6, 8 and 10 microseconds.

[0057] The results showed that, although color images were formed on thereceptor at the four different pulse widths, the images were discolored.A microscopic examination of the images revealed that the red colorimages were contaminated with the black aluminum light-to-heatconversion layer which had transferred from the donor.

Example 2

[0058] This example demonstrates the preparation and use of a thermaltransfer donor with a thermoset interlayer.

[0059] The same black aluminum light-to-heat conversion layer referencedin Example 1 was coated with a 5 weight % solution of hydantoinhexacrylate (49 parts by weight), 1,6-hexanediol diacrylate (49 parts byweight) and 2,2-dimethoxy-2-phenylacetophenone (2 parts by weight) in2-butanone using a #5 coating rod, dried and then radiation crosslinkedvia exposure in a Radiation Polymer Corporation (Plainfield, Ill.) UVProcessor Model No. QC 1202AN3TR. (medium pressure uv lamp, totalexposure ca. 100 millijoules/cm², N₂ atmosphere) to produce aninterlayer. The cured interlayer was smooth, non-tacky, and resistant tomany organic solvents including 2-butanone. The cured interlayer wasthen overcoated with the same red color ink employing the same coatingprocedures as described in Example 1.

[0060] The resulting donor was tested for transfer of the thermaltransfer layer to a glass slide receptor employing laser imagingconditions identical to those described in Example 1.

[0061] A microscopic examination of the images on the receptor clearlyindicated that the red color images were free of black aluminumcontamination. The same microscopic examination of the imaged area ofthe donor showed that the interlayer and black aluminum light-to-heatconversion layer remained intact on the thermal transfer donor.

Example 3

[0062] This example demonstrates the preparation and use of a thermaltransfer donor with a thermoplastic interlayer.

[0063] The same black aluminum light-to-heat conversion layer referencedin Example 1 was coated with a 10 weight % solution of Radel A-100polysulfone resin (Amoco Performance Products, Inc., Alpharetta, Ga.) in1,1,2-trichloroethane using a #12 coating rod. The Kadel A- 100interlayer was then overcoated with the same red color ink and employingthe same coating procedures as described in Example 1.

[0064] The resulting donor was tested for transfer of the thermaltransfer layer to a glass slide receptor employing laser imagingconditions identical to that described in Example 1. The results againshowed that the color images were formed on the receptor at the fourdifferent pulse widths. A microscopic examination of the images on thereceptor clearly indicated that the red color images were free of blackaluminum contamination. The same microscopic examination of the imagedarea of the donor showed again that the interlayer and black aluminumlight-to-heat conversion layer remained intact on the thermal transferdonor.

Example 4

[0065] This example demonstrates the preparation and use of a thermaltransfer donor with an inorganic interlayer.

[0066] A black aluminum (AlO_(X)) coating was deposited onto 4 milpoly(ethylene terephthalate) (PET) substrate via evaporation oral in apartial O₂ atmosphere according to the teachings of U.S. Pat. No.4,430,366. The transmission and reflection spectra of the resultantcoating on PET were measured from both the black aluminum coating sideand the substrate (PET) side using a Shimadzu MPC-3100 spectrophotometerwith an integrating sphere (Shimadzu Scientific Instruments, Inc.,Columbia, Md.). The transmission optical densities (TOD -logT, where Tis the measured fractional transmission) and reflection opticaldensities (ROD=−logR, where R is the measured fractional reflectance) at1060 nm are listed in Table 1. The thickness of the black aluminumcoating was determined to be 1100 Å by profilometry after masking andetching a portion of the coating with 20 percent by weight aqueoussodium hydroxide. TABLE 1 TOD ROD Side of Incident Beam (at 1060 nm) (at1060 nm) Coating 1.047 0.427 Substrate 1.050 0.456

[0067] An alumina interlayer (approximately 1000 Å thick) was coatedonto the black aluminum surface by evaporation of Al₂ O₃ in a vacuumcoater.

[0068] A colorant coating solution was prepared by combining and mixing2 grams of 10 weight % Heucotech GW3451 Lot 3F2299 PG 7 binderlesspigment dispersion (Heucotech, Ltd., Fairless Hills, Pa.), 0.917 gramsdeionized H₂ O 0.833 grams of 18 weight % Elvacite® 2776 in water(prepared by mixing 0.8 g of a 25% ammonia solution and 22 g water, and5 g of Elvacite® 2776 from ICI Acrylics, Wilmington, Del.) and 10 dropsof a 1 weight % solution of FC-170C fluorochemical surfactant (3M, St.Paul, Minn.). This green coating solution was coated onto the aluminasurface using a #4 coating rod. The resultant green donor media wasdried at 50° C. for 2 minutes. The same green solution was coated ontothe black aluminum (AlO_(X)) surface of the light-to-heat conversionfilm that did not have the alumina interlayer using #4 coating rod. Theresultant green donor media was dried at 50° C. for 2 minutes.

[0069] These two donors, one with an alumina interlayer and the otherwithout, were imaged onto glass receptors to make color filter elementsfor a liquid crystal display via laser induced thermal transfer imaging(LITI) utilizing the above-described Laser Imaging Procedure A. Forthese experiments, the laser spot diameter size (1/e²) was 100 μm, thepower at the film plane was 4.2 Watts, and the pulse width was 8 μsec.The amount of black aluminum contamination of the resultant colorfilters was then quantified via digitizing micrographs of thecorresponding color filters and subsequent image analysis with IPLABSpectrum-NV (Signal Analytics Corp., Vienna, Va.). The analyses indicatethat the average area of the black aluminum light-to-heat conversionlayer transferred to the receptor per imaged spot was 4 μm² blackaluminum contamination per spot for the sample with the aluminainterlayer vs. 125 μm² for the sample with no interlayer.

[0070] These results demonstrate the efficacy of the interlayer inimproving transferred image quality and preventing image contaminationwith the light-to-heat conversion layer.

Example 5

[0071] This example demonstrates the preparation and use of a thermaltransfer donor with a thermoset interlayer and a crosslinkable transferlayer.

[0072] A carbon black light-to-heat conversion layer was prepared bycoating an aqueous dispersion of carbon black in a radiation curableresin onto a 2 mil PET substrate with a Yasui Seiki Lab Coater, ModelCAG-150 (Yasui Seiki Co., Bloomington, Ind.) using a microgravure rollof 90 helical cells per lineal inch. The coating was subsequentlyin-line dried and uv-cured on the coater before windup. The coatingsolution consisted of 16.78 weight % of a urethane-acrylate oligomer(Neorad NR-440 from Zeneca Resins, Wilmington, Mass.), 0.84 weight % of2-hydroxy-2-methyl-1-phenyl-1-propanone photoinitiator (Darocur 1173,Ciba-Geigy, Hawthorne, N.Y.), 2.38 weight % of carbon black (SunsperseBlack 7, Sun Chemical, Amelia, Ohio), and 80 weight % of water having apH of ca. 8.5.

[0073] The light-to-heat conversion layer was then overcoated with aninterlayer coating utilizing the above-described coater with amicrogravure roll of 110 helical cells per lineal inch. After theinterlayer was coated, it was in-line dried and uv-cured. The interlayercoating solution consisted of 19.8 weight % of a urethane-acrylateoligomer (Neorad NR-440 from Zeneca Resins, Wilmington, Mass.), 1.0weight % of 2-hydroxy-2 methyl-1-phenyl-1-propanone photoinitiator(Darocur 1173, Ciba-Geigy, Hawthorne, N.Y.), and 79.2 weight % of waterhaving a pH of 8.5.

[0074] The colorant transfer layer was a 15 weight % nonvolatilescontent aqueous dispersion prepared by Penn Color, Doylestown, Pa., andconsisted of Pigment Green 7 and Elvacite 2776 (ICI Acrylics, Inc.,Wilmington, Del.) neutralized with dimethylethanolamine at a 3:2pigment/binder ratio, containing 4 weight % Primid XL-552 (EMS AmericanGrilon, Sumter, S.C.) relative to the polymer, and 1 weight % TritonX-100 relative to the total nonvolatiles content. This dispersion wascoated onto the interlayer using a #3 coating rod and the resultantcoating was dried at 80° C. for 3 minutes.

[0075] The colorant layer was then transferred to two glass slides usingimaging conditions employing Laser Imaging Procedure B to produce LCDcolor filter elements. The colorant transferred to the glass slides(lines ca. 90 micrometers wide with a line-to-line spacing of ca. 150micrometers) with no contamination of the carbon black layer.Microscopic examination of the donor sheet showed the carbon blackcomposite light-to-heat conversion layer and the protective clearinterlayer were intact. One of the color filter elements was then placedin an oven and heated at 200° C. in a nitrogen atmosphere for one hourin order to activate the crosslinking chemistry between the Primid XL552and the Elvacite 2776. The other color filter element was not heated,but maintained at ambient temperature. Each of the resultant colorfilter elements was then cut into three ca. 25 mm×37 mm sections. One ofthe sections derived from each of these color filter elements was thenimmersed in 10 ml of 1-methyl-2-pyrrolidinone for 10 minutes. The colorfilter elements were then removed from the immersion solvents. Thevisible spectra of the solutions resulting from extractions of thesecolor filter elements were then obtained in a quartz cuvette with a 1 cmpath length on a Shimadzu MPC-3100 spectrophotometer. These spectraindicated the λ_(max) of the color cell array extracts to be at ca. 629nm, with good chemical resistance of each of the color cell arrayelements corresponding to low absorbance of its 1-methyl-2-pyrrolidinoneextract at 629 nm. The corresponding results of the chemical resistancetesting of the crosslinked and uncrosslinked color filter element areprovided in Table 2. TABLE 2 Color Filter Element Absorbance ofCorresponding 1-Methyl-2- Designation Pyrrolidinone Extract (629 nm)uncrosslinked color array 0.53 crosslinked color array 0.04 neat solvent(1-methyl-2- 0.04 pyrrolidinone)

[0076] The above results demonstrate the efficacy of the interlayer inimproving the quality of the transferred image and the effectiveness ofcrosslinking the transferred coating to improve its correspondingsolvent resistance.

Example 6

[0077] (Comparative Example)

[0078] This example demonstrates the preparation and use of a thermaltransfer donor without an interlayer.

[0079] A carbon black light-to-heat conversion film with an absorbanceof 1.35 at 1064 nm, was prepared by coating an aqueous dispersion ofcarbon black in a radiation curable resin onto a 2 mil PET substratewith a Yasui Seiki Lab Coater, Model CAG-150 (Yasui Seiki Co.,Bloomington, Ind.) using a microgravure roll of 90 helical cells perlineal inch. The coating was subsequently in-line dried and uv-cured onthe coater before windup. The coating solution consisted of 1 part ofcarbon black (Sunsperse black, Sun Chemical, Amelia, Ohio), 7 parts ofNR-440 (a crosslinkable urethane acrylate oligomer from Zeneca Resins,Wilmington, Mass.), and 0.35 part of a photoinitiator (Darocur 1173 fromCiba-Geigy, Hawthorne, N.Y.) at 35 wt % total solid in water to give alight-to-heat conversion coating with a 4.5 μm dry thickness.

[0080] The light-to-heat conversion layer was overcoated with a clearinterlayer, followed by a colorant layer. Using a #5 coating rod, anaqueous solution containing 12.5 wt % NR-440 and 0.6 wt % Darocur 1173was coated, dried at 80° C. for 2 minutes and UV crosslinked to providea color topcoat with a heat stable, smooth release surface. The colortransfer layer was applied by coating the green color ink of Example 5at 15 wt % total solid using a #5 coating rod and drying for 3 min at60° C. to give a 1 μm thick colorant layer.

[0081] The donor thus prepared was tested for imagewise transfer of thethermal transfer layer to a black chrome coated glass receptor, whichhad an absorbance of 2.8 at 1064 nm. The color donor sheet was imagedwith a line pattern and transferred onto the glass receptor (75 mm×50mm×1.1 mm). Imaging was performed in a flat-bed imaging system, using aNd:YAG laser operating at 7.5 W on the donor film plane with a 140 μmlaser spot size (1/e² diameter). The laser scan rate was 4.5 m/s. Imagedata were transferred from a mass-memory system and supplied to anacoustic-optic modulator which performed the imagewise modulation of thelaser. During the imaging process, the donor sheet and the receptor wereheld in intimate contact with vacuum assistance.

[0082] A microscopic inspection of the resultant image on the receptorindicated that the imaged lines possessed a uniform line width of 89 μm.Damage (e.g., roughened surface, cracks, bubbles, color variation, etc.)was observed to be present at the central portion of each of thetransferred colorant lines.

Example 7

[0083] This example demonstrates the preparation and use of a thermaltransfer donor with a vapor-coated aluminum reflective interlayer coatedover a LTHC layer comprising carbon black dispersed in a crosslinkedorganic binder.

[0084] The donor used in this example was the same as that used inExample 6, except that a vapor-coated aluminum reflective interlayer wascoated on the light-to-heat conversion layer prior to coating the colortransfer layer. The aluminum coating was determined to have 85.8%reflection at 1064 nm.

[0085] The donor was tested for imagewise transfer of the thermaltransfer layer to a black chrome coated glass receptor using the samemethod described in Example 6. A microscopic inspection of the resultantimage indicated that the image lines were of good overall quality with auniform line width of 82 μm. No obvious sign of thermal damage wasobserved in the central portion of the transferred lines.

Example 8

[0086] This example demonstrates the preparation and use of a thermaltransfer donor with a white reflective interlayer.

[0087] The donor used in this example was the same as that used inExample 6, except that a white reflective interlayer was coated on thelight-to-heat conversion layer prior to the other coatings. The whitereflective layer was prepared by coating a white correction ink at 17.3wt % total solid (Pentel Correction Pen™ ink) with a #3 coating rod,followed by drying at 80° C. for 2 min. The coating was determined tohave a reflectivity of 22.5% at 1064 nm.

[0088] The donor was tested for imagewise transfer of the thermaltransfer layer to a black chrome coated glass receptor using the samemethod described in Example 6. A microscopic inspection of the resultantimage indicated that the image lines were of good overall quality with auniform line width of 82 μm. No obvious sign of thermal damage wasobserved in the central portion of the transferred lines.

Example 9

[0089] The donors used in this example were the same as those used inExamples 6-8, except that a carbon black light-to-heat conversion layerwith an absorbance of 0.94 at 1060 nm was used. This light-to-heatconversion layer was prepared by the same method as described in Example6, except that the coating solution contained 27 wt % total solidsinstead of 35 wt %.

[0090] The donors were tested for imagewise transfer of the thermaltransfer layer to a black chrome coated glass receptor using the samemethod described in Example 6.

[0091] The results of a microscopic inspection of the resultant imageson the receptors are summarized in Table 3. TABLE 3 Effect of ReflectiveInterlayer on Image Quality (5.3 m/sec Scan Speed) Donor Linewidth (μm)Damage to transferred line Control  90 some Al Interlayer  97 some WhiteInterlayer 100 none

[0092] The results indicate that images transferred from the donor witha white interlayer (22.5% R, 46% T) suffered the least damage.

[0093] These results demonstrate the efficacy of a reflective interlayerin the improvement of transferred image quality and the prevention ofthermal damage of the transferred material.

Example 10

[0094] This example demonstrates the preparation and use of a thermaltransfer donor with a reflective aluminum interlayer coated over a blackaluminum LTHC layer. A black aluminum (partially oxidized Al, AlO_(X))light-to-heat conversion layer of approximately 800 Å was coated onto a4 mil poly(ethylene terephthalate) (PET) substrate via reactivesputtering of Al in an Ar/O₂ atmosphere in a continuous vacuum coateraccording to the teachings of U.S. Pat. No. 4,430,366. Approximately 100Å of Al was then sputtered onto the AlO_(X) light-to-heat conversionlayer in an Ar atmosphere with the same continuous vacuum coater. Theresultant material containing the reflective aluminum interlayer wasthen overcoated with an aqueous green color ink of the composition shownin Table 4 using a #4 coating rod and dried at 60° C. to produce athermal transfer donor. TABLE 4 Composition of Aqueous Green Ink CoatingSolution Coating Component Percent by Weight PG-7 Pigment* 9.1 ICIElvacite 2776* 53 Triethyl-O-acetyl-citrate 0.3 Dimethylethanolamine 1.13M FC-430 Surfactant 0.04 H₂O 84.2

[0095] This donor was then tested for thermal transfer to a glass slidereceptor to produce a color filter element for a liquid crystal display.The above-described Laser Imaging Procedure A was employed and the laserspot diameter was 100 μm (1 /e²), the power at the film plane was 8.4Watts, and exposures were performed at pulse widths of 4, 6 and 8microseconds.

[0096] The results showed that the transferred images were essentiallyfree from black aluminum contamination under the above-described imagingconditions.

[0097] Reasonable variations and modifications are possible from theforegoing disclosure without departing from either the spirit or scopeof the present invention as recited in the claims.

What is claimed is:
 1. A thermal transfer element comprising: a thermaltransfer layer comprising a binder and a plasticizer; a light-to-heatconversion layer comprising a material that absorbs imaging radiation toconvert the radiation into heat; and an interlayer coated between thelight-to-heat conversion layer and the transfer layer, wherein theinterlayer remains substantially intact when the thermal transferelement is exposed to imaging radiation to selectively transfer thethermal transfer layer.
 2. The thermal transfer element of claim 1 ,wherein the thermal transfer layer further comprises a colorant disposedin the binder.
 3. The thermal transfer element of claim 2 , wherein thecolorant comprises a pigment.
 4. The thermal transfer element of claim 2, wherein the colorant comprises a dye.
 5. The thermal transfer elementof claim 1 , wherein the binder comprises a thermoplastic.
 6. Thethermal transfer element of claim 1 , wherein the binder iscrosslinkable.
 7. A thermal transfer element comprising: a thermaltransfer layer capable of being selectively transferred from the thermaltransfer donor element when the thermal transfer donor element isexposed to imaging radiation; a light-to-heat conversion layercomprising a material that absorbs imaging radiation to convert theradiation into heat; and an interlayer disposed between thelight-to-heat conversion layer and the transfer layer, the interlayerbeing absorptive of imaging radiation, wherein the interlayer remainssubstantially intact when the thermal transfer element is exposed toimaging radiation to selectively transfer the thermal transfer layer. 8.The thermal transfer element of claim 7 , further comprising a secondinterlayer disposed between the absorptive interlayer and the transferlayer.
 9. The thermal transfer element of claim 8 , wherein the secondinterlayer remains substantially intact when the thermal transfer layeris selectively transferred upon exposure of the thermal transfer elementto imaging radiation.
 10. A thermal transfer element comprising: athermal transfer layer capable of being selectively transferred from thethermal transfer donor element when the thermal transfer donor elementis exposed to imaging radiation; a light-to-heat conversion layercomprising a material that absorbs imaging radiation to convert theradiation into heat; and two or more interlayers disposed between thelight-to-heat conversion layer and the transfer layer, at least one ofthe interlayers being absorptive or reflective of imaging radiation, andat least another of the interlayers being transmissive of imagingradiation, wherein the interlayers remains substantially intact when thethermal transfer element is exposed to imaging radiation to selectivelytransfer the thermal transfer layer.